In a fuel injection system for a spark ignition, internal combustion engine, it is necessary that each fuel injector, such as an electromagnetic fuel injector, used in such an injector system be operative to precisely control the amount of fuel being injected as a function of engine operation. Thus it is important that the pressure of the fuel being supplied to such an intermittently opening injection valve be maintained substantially constant.
It is also important that each such fuel injector be accurately calibrated prior to its installation in the fuel injection system for an engine. This calibration is required to insure that the injector will be operative, as desired, to accurately meter a predetermined quantity of fuel as a function of the opening time of the valve of the injector.
This calibration of each injector can be done by a selective fit approach during assembly of the injector whereby to regulate the injector stroke or, as disclosed in co-pending United States patent application Ser. No. 941,754 entitled "Electromagnetic Fuel Injector" filed Sept. 13, 1978 in the name of James D. Palma and assigned to a common assignee, the structure of the fuel injector is such whereby the injector stroke can be adjusted, as desired, while flowing a calibration fluid on a continuous basis through the injector.
In this latter method of calibration, it is particularly important that the pressure of the calibration fluid flowing through the injector be maintained as constant as possible as by means of a pressure regulator. Otherwise, any variation in the pressure of the calibration fluid will effect the accuracy of calibration of the fuel injector. Thus the performance of a pressure regulator in maintaining a constant predetermined pressure during such calibration of an injector is of particular importance to insure correct initial calibration of the fuel injector.
However, the known prior art pressure regulators are not capable of maintaining the pressure of a fluid within very low pressure tolerance limits for the calibration requirements of a fuel injector, since such known prior art pressure regulators are all subject to regulator "gain". Regulator "gain" is defined as the regulator pressure change per unit fluid flow change through the regulator assembly. In the use of such a pressure regulator to control the pressure of a calibration fluid during calibration of a fuel injector, it will be apparent that the desired regulator gain values for such a pressure regulator should be as low as possible, preferably zero.
Accordingly, a primary object of the present invention is to provide an improved, diaphragm controlled, pressure regulator that is adapted to accurately control the pressure of fluid flowing to a fuel injector, independent of the amount of fluid flowing through the pressure regulator.
Another object of the invention is to provide an improved, diaphragm controlled, pressure regulator whereby a trim control pressure can be applied to the side of the diaphragm opposite the pressure regulated side of the diaphragm whereby the mean pressure of the regulated fluid can be accurately maintained.
A further object of the present invention is to provide an improved, diaphragm controlled, pressure regulator that is operative in a manner whereby the controlled pressure can be accurately maintained without substantial regulator gain irrespective of the rate of fluid flow through the pressure regulator.
Still another object of the present invention is to provide an improved, diaphragm controlled, pressure regulator wherein a variable height standpipe is used to provide a control trim pressure to one side of the diaphragm so that the normal gain of such a pressure regulator is reduced to substantially zero.
For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings.